It is known that heavy crude oils contain corrosive materials such as organic acids, carbon dioxide, hydrogen sulfide, and chlorides, etc., but seldom do they constitute a serious corrosion problem. However, a few crudes contain sufficient quantities of organic acid, generally naphthenic acids, that cause severe corrosion problems. The term naphthenic acid generally refers collectively to all of the organic acids present in crude oils. In some petrochemical applications, hydrofluoric acid (HF) is a commonly used material, e.g., it is used as a catalyst in alkylation units of refineries. In other petrochemical applications, sulfuric acid is a common corrosion problem.
In petroleum applications, materials with high Cr and Mo content are employed for their naphthenic acid corrosion resistant properties, with a minimum of 9% Cr being typically used for severe attacks (e.g., 316SS has nominally 18% Cr and 2% Mo min.). In other applications, nickel alloys are used for the handling of hydrofluoric acid.
Stating in the early 1990's, a large number of bulk metallic glasses (BMG), based mainly on Zr—, Cu—, Hf—, Fe— and other metals were developed. These materials are characterized as having excellent mechanical properties, in particular high strength and large elastic domain at room temperature, as compared to the conventional metallic alloys. Surface treatment of BMG materials is known. U.S. Patent Publication No. 2008/0041502 discloses a method for forming a hardened surface, wherein a metallic glass coating layer is heated to a temperature of 600° C. to less than the melting temperature of the alloy. The post treatment of the metallic coating is utilized to transform only the surface of the coating material, partially devitrifying the coating layer. U.S. Patent Publication No. 2004/0253381 discloses treating an amorphous metal layer, wherein the glass is put through a simple annealing. Again, only the amorphous coating layer properties are modified in the process.
There is still the need for an improved method to surface treat metallic glass coating for improved properties, which method also improves the properties of the substrate layer underlying the metallic glass coating, for coatings with improved corrosion, wear, erosion and abrasion resistance properties for petroleum-related applications. There is also a need for improved methods to treat amorphous metal (or BMG) coatings, devitrified BMG nanostructured coatings, and surface modifications in general. There is also the need for a method to improve corrosion resistant properties by surface treatment, specifically by gradually intermixing a BMG coating (or BMG-like coating) with the underlying substrate for improved corrosion, wear and abrasion resistance.